Western European Nuclear Regulators Association (WENRA) has recommended that all European nuclear reactor pressure vessels undergo standardised reviews.

The agency’s action comes after ultrasound uncovered fractures at Belgium’s Doel 3 and Tihange 2 units last year.

Further investigations by owner Electrabel indicated that these were so-called hydrogen “flakes” introduced during the manufacturing process. The plants remained offline until Belgium’s Federal Agency for Nuclear Control concluded that the inclusions were of no safety significance and approved their re-activation in May this year.

Doel 3

The vessels for Doel 3 and Tihange 2 were produced by Rotterdam Drydock Company (RDM). As many as 21 reactor pressure vessels made by RDM are located around the world. National nuclear safety authorities immediately ordered inspections of those units, but no similar inclusions were found.

World Nuclear News reports that the agency has called for a standardized, two-step review procedure. Firstly, operators should conduct a comprehensive review of the vessel manufacturing and inspection records. Secondly, if the national nuclear safety authority considers it necessary based on the results of first stage, examination of the vessels should be undertaken using non-destructive testing (NDT) technology.

These NDT examinations – which can be carried out during scheduled outages – should cover a representative volume of vessel forging base material in areas known to be potentially susceptible to hydrogen flaking, WENRA suggested. If these inspections reveal evidence of hydrogen flaking, the inspections should be extended appropriately, it said.

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